In Western or Eastern cultures, in music-related fields, many musical instruments have a sound box structure that can facilitate to adjust the quality and volume of the instrument. For example, many electronic musical instruments, percussion instruments or string instruments have similar sound box structures.
String instruments play an important role in many kinds of musical instruments. One of the most famous instruments in the Western is the violin. Even modern eastern Chinese music has also introduced the Western violoncello as one key instrument in bass performance. In general, the structure of string instruments is mainly composed of boards with different curvatures to make a structure of the sound box, and the sound post plays an important role in affecting the sound quality and volume of the string instrument.
Usually, a sound box of the string instrument is composed of a top board (roof), a bottom board (back plate) and a side board. For violin instrument, there is a curvature profile on the top board and the bottom board. The sound post is mounted between the top board and the bottom board.
The location of the sound post is mainly located on an area below the bridge of violin instrument. The bridge is usually made of a piece of wood in a special shape, which mainly transmits vibration of the strings to the sound box to produce sound. In the traditionally manufacturing process, the sound post is a wooden cylinder, with specific length and shape of its two ends fitted to the sound box against the top board and the bottom board. Because the top board and the bottom board usually have a certain curvature, it is usually necessary to constantly cut the two ends of the sound post to fit to the shape of the top board and the bottom board in the sound box during installing the sound post.
The sound post can effectively improve the stability and sound quality of string instruments. For a violin, the sound post can only be mounted through the sole opening, f-hole, of the sound box. Therefore, it is a time-consuming and labor-consuming process to cut the sound post manually and gradually install it into the sound box of string instruments. Therefore, some people have developed a sound post structure which can adjust the length of the sound post or the curvature of the top board and the bottom board of the sound box after the sound post is introduced into the f hole. However, when adjusting the length and position of such a sound post, it still needs external tools to penetrate the f hole for more precise operation. As a result, in addition to the considerable increase in operational difficulty, the tool structure used to adjust the length of the sound post is also complicated.
Moreover, when the tightness of the sound post against the top board and the bottom board changes, there is a need to adjust the sound post at any time due to the corresponding changes of timbre of the instrument. However, when this situation occurs, there is no a professional adjustment tool at hand, it will cause inconvenience in use.